Different levels of COX-1 and COX-2 enzymes in synoviocytes and chondrocytes during joint contracture formation.

ABSTRACT

OBJECTIVE: To measure the levels of prostaglandin endoperoxide H synthase (PGHS) isozymes (or cyclooxygenase, COX) in vivo during the development of joint contractures secondary to immobilization in rats. METHODS: Rats had one knee joint immobilized for up to 32 weeks. Three groups were compared 47 rats had knee joints immobilized, 38 animals had sham surgery, and 13 unoperated animals served as controls. Levels of PGHS-1 and PGHS-2 enzymes were characterized in the chondrocytes and synoviocytes of the knee joint by immunohistochemistry. Immunostaining intensity was quantified by microscopy using conventional analysis. RESULTS: PGHS-1 level was lower in synoviocytes of the anterior capsule compared with shams (1.3 vs 2.0; p < 0.05). PGHS-2 level was also lower in synoviocytes of the posterior capsule (1.8 vs 2.3; p < 0.05), but higher in chondrocytes at the anterior aspect of the tibia compared with shams (1.6 vs 0.8; p < 0.05). PGHS-2 staining was increased in chondrocytes at the posterior, opposed, and anterior aspects of the tibia compared with controls (1.1, 0.6, 0.8 vs 0.2, 0.1, 0.2, respectively; all p < 0.05). CONCLUSION: Immobility induced joint contractures are characterized by a contrasting cellular pattern of PGHS enzyme levels decreased in the synovium and increased in the chondrocytes. These findings suggest that chondrocytic PGHS isoenzymes are important in cartilage degradation of contractured joints.